Transportable refrigeration unit having induction alternator-induction motor reconnection and control system

ABSTRACT

This invention relates to a transportable refrigeration unit having two modes of operation and more particularly to such a refrigeration unit having an induction machine that may function as a prime mover or as a generator of electric power after the proper connection to an appropriate receptacle has been made with a power cord which is connected to the induction machine and is adapted to be received by either a receptacle that is attached to the unit and has passive electrical components so connected thereto for converting the induction machine to an electric generator or to be received by an external electric power source receptacle without passive components connected thereto when the induction machine is to function as a prime mover.

lllniten i States tent 1 Martin et all.

Wilt/larch i3, i973 Inventors: Robert L. Martin, Excelsior; Leland L.Howlantl, Rosemount; LeRoy .ll. lllichinger, St. Paul, all of Minn.

Thermo King Corporation, Minneapolis, Minn,

Filed: Oct. 7, 1971 Appl No.: 187,434

Assignee:

US. Cl ..307/68, 62/236 int. Cl. .Hillf 1/00 Field of Search ..307/68,47, 64, 65, 66, 67;

References Cited UNITED STATES PATENTS 5 1970 White "62/236 x PrimaryExaminer-Herman J. Hohauser Attorney-F. H. Henson et al.

[57] ABSTRACT This invention relatesto a transportable refrigerationunit having two modes of operation and more particularly to such arefrigeration unit having an induction machine that may function as aprime mover or as a generator of electric power after the properconnection to an appropriate receptacle has been made with a power cordwhich is connected to the induction machine and is adapted to bereceived by either a receptacle that is attached to the unit and haspassive electrical components so connected thereto for converting theinduction machine to an electric generator or to be received by anexternal electric power source receptacle without passive componentsconnected thereto when the induction machine is to function as a primemover.

5 Claims, 2 Drawing Figures TRANSPORTABLE REFRIGERATION UNIT EXTERNALPOWER SOURCE CENTRIFUGAL CL CH l 2 l ELECTRIC HEATERS TRANSPORTABLEATTACHED RECEPTACLE l l it T0 ENGINE CONTROL CIRCUITS SHE EI 10F 2PATENTEDHAR 1 31915 2.50% 552 wzazw E wmmckmz PATENTEUMAR 1 3191s SHEEI2 OF 2 w l w SUPPLY POWER 460 V.A.C. 3 PHASE TANK HEATERS DEFROST FAN lTIMER I UGHT I l I EVAP FAN comcrpn Y u d R m mm 2 R G 9.. AE N TN mL 3m N U B 2 N 5 2 A R K B m m WA A B m O T m S O M R E H T F R 2 Mm EL m50 A 2 p STARTER RELAY IGN. COILS DEFROST RELAY COMP CONT FIG. 2

CROSS REFERENCES TO RELATED APPLICATIONS So far as known, this inventionis not related to any pending patent application.

BACKGROUND OF THE INVENTION It has been the custom in usingtransportable refrigeration units to provide a self contained privemover or or other mechanical power source to drive both the compressorand the electric power generator of the unit. However, when'the vehiclewhich provides the transportation is required to remain stationary forlong periods of time, or when the units are containers on board a ship,or when refrigerated trailers are stationary at the loading dock, it isdesirable to power the refrigeration units entirely from availableexternal electric power without running the self contained prime moversuch as an internal combustion engine or the like.

As stated above, it is therefore required that an alternate externalsource of electric power be available in order to continue the operationof the refrigeration unit and prevent the goods from spoiling. Forsystems of this type, a transportable refrigeration unit is providedwhich uses an induction 'machine both as a prime mover and alternativelyas an engine driven auxiliary electric power generator when driven bythe self contained prime mover. Such a system would be improved if itcould eliminate the need for complicated switching arrangements whichmustbe actuated whenever conditioning the unit to be operable from aself-contained source of prime mover power or from the alternateexternal electric power source. It would be most desirable to employ aconditioning means for a refrigeration unit which is simple but providesboth reliable and safe electrical connections regardless of the skill ofthe user.

PRIOR ART References may be made to the following United States patentswhich disclose a transportable refrigeration unit that may be poweredeither from an internal prime mover or from an external electric powersource by converting an induction machine from a generator to anelectric motor to drive the unit:

U.S. Pat. No. 2,907,182 Kuklinski issued Oct.

U.S. Pat. No. 3,043,l l Hatter issued July l0,

However, neither of the above patents discloses a transportablerefrigeration unit employing an inductionv machine functioning as aprime mover which maybe converted into a generator of electric powerdepending primarily upon the connection ofa power cord which is adaptedto be received by either a receptable which is self contained within theportable unit having passive electrical components or by a receptaclewhich is an external source of electric power.

SUMMARY OF THE INVENTION In order to provide an alternate source ofpower to drive a transportable refrigeration unit, the refrigerationunit is made capable of having two modes of operation. The unit ispowered by a self contained prime mover in the first mode of operationand from the receptacle of an external power source during the secondmode of operation. Mechanical means are provided to enable the primemover to be connected to a compressor and to an induction machinefunctioning as a generator in the first mode of operation. Themechanical means also enable the prime mover to be disconnected from thecompressor and induction machine during the second mode of operation. Apower cord and plug, which is connected from the induction machine tothe electrical loads during both first and second modes of operation, isadapted to be received during the first mode by a receptacle attached tothe refrigeration unit and having passive electrical components. Thisenables the induction machine to function as a self excited generator ofelectric power for supplying power to the electric load during the firstmode of operation. The plug is also adapted to be connected to theexternal power source receptacle to power both the electrical loads andthe induction machine as a prime mover or motor in the second mode ofoperation. Tl-Iis latter connection enables the induction machine tofunction as a second prime mover to drive the compressor during thesecond mode of operation when the self contained prime mover is not inoperation.

BRIEF DESCRIPTION OF DRAWINGS FIG. l is a block diagram of the overalltransportable refrigeration unit and an external power sourcereceptacle; and

FIG. 2 is a schematic circuit diagram illustrating the engine controland conditioning means of the transportable refrigeration unit.

DESCRIPTION OF PREFERRED EMBODIMENT Referring to FIG. 1 of the drawings,a transportable refrigeration unit is shown which is capable of twomodes of operation. The first mode of operation is to be utilized when arefrigerated cargo is being transported. In this first mode, a selfcontained prime mover such as an internal combustion engine 1 isconnected to both a refrigerant compressor 3 and a main drive inductionmachine or motor-generator 4 by means of a centrifugal clutch 2, thepurpose of engine 1 being to provide a power source to drive bothcompressor 3 and induction motor-generator 4. It is within the scope ofthis invention to employ a steam turbine or any other suitable primemover in this place of internal combustion engine 1. In the preferredform of this invention, induction machine 4 is an alternating current,motor-generator, although any induction machine having both motor andgenerator capabilities may be employed. The induction motor-generator isconnected by means of a portable four conductor power cord or equivalentcable 7 and plug 6 to a receptacle 8 which is attached to thetransportable unit and is adapted to receive the power plug 6. Theattached receptacle 8, is provided with a bank of capacitors 9 or othersuitable passive electrical components connected in delta configurationto three contact wire terminals of the attached receptacle 8. Thecapacitor bank 9 supplies sufficient excitation for the start up andfunctioning of motor-generator 4 as an engine driven, self excitedinduction generator, such as an alternator, during the first mode ofoperation. A fourth wire contact terminal ll of the attached receptacle8 may be connected to the engine control circuit to assure that onlyafter the power plug 6 has been properly received by the attachedreceptacle 8 can engine 1 be conditioned to start, thus providing abuilt in safety feature when using the refrigeration unit in the firstmode. Such engine control circuit and conditioning means will be morefully explained hereinafter.

As already disclosed, when power plug 6 is connected to receptacle 8 inthe first mode of operation, the induction motor-generator 4 willfunction as a self excited generator of electric power which will thenbe capable of driving the electrical loads of the transportablerefrigeration unit such as the fan motor and the electric resistancedefrost heaters 15. Means are provided for connecting the electricalloads 5 and and the compressor 3 to the power cable 7 in both the firstand second modes of operation. Heat contactors HC provide the meanswhereby the heaters 15 may be connected to the power cable in order todefrost the refrigeration units while the compressor 3 and fan motor 5are not operating. Main contactors MC provide the means wherebycompressor 3 may be periodically connected to power cable 7 during acycling operation or where it becomes necessary to energize the fanmotor 5 while the compressor is cycled on and off in order to regulatethe amount of cold air flowing within the unit. Fan contactors FCprovide the means whereby the fan motor 5 may be connected to the powercable 7 to drive a fan (not shown) in order to pass air through theevaporator coil (not shown) in heat exchange relationship with therefrigerant expanding from the compressor 3.

When the refrigerated container remains stationary for extended periodsof time, where external electric power is available, it may becomedesirable to cease operating the self contained engine 1. In order tocontinue refrigerating the vehicle compartment, the external source ofelectric power must be arranged to power the compressor 3 and electricalloads 5 and 15 of the unit. The transportable refrigeration unittherefore will operate in the second mode of operation where it is to bepowered by an alternate, external electric source. When engine 1 is shutdown, it is mechanically disconnected from the compressor 3 andinduction motorgenerator 4 by means of centrifugal clutch 2 or otherclutch device. The refrigeration unit may be simply and safely convertedto operate from the alternate source of electric power during the secondmode of operation by connecting power plug 6 to the external electricpower receptacle 10. The external receptacle 10, which may be located ata loading dock, or on a pier, or on ship board, supplies 30,AC power toelectric loads 5 and 15 by wayof power cable 7. Electric power is alsosupplied to the induction motor-generator 4 which becomes conditioned tooperate as a prime mover or, in the preferred case, as a motor duringthe second mode of operation. The induction motor 4 is now capable ofdriving the unit compressor 3 in the second mode of operation in orderthat refrigeration of the vehicle compartment may continue while thevehicle is at standstill and the self contained engine 1 is at rest.

FIG. 2 of the drawings shows the conditioning and control means for theinternal combustion engine of the transportable refrigeration unit.During the first mode of operation when the unit is being driven by aself contained internal combustion engine, power plug 6 is connected toattached receptacle 8. Capacitor bank 9, connected to three contact wireterminals of power plug 8, provides sufficient excitation to enableinduction motor-generator 4 to operate as an engine driven, self excitedinduction alternator to generate power for electrical loads 5 and 15.Change over relay 20 is electrically connected from the fourth wire 11of plug 8 to the engine control circuitry. Change over relay 20 must beactuated in order to provide conditioning means for the internalcombustion engine to start during the first mode of operation. Thechange over relay 20 incorporates a safety feature within the unit,whereas, without proper connection of power plug 6 to attachedreceptacle 8, change over relay 20 cannot be actuated thus preventingthe engine starting circuit from becoming energized.

To commence operation of the self contained engine in the first mode ofoperation, on-off switch 21 is moved to the on position. Closing switch21 enables 12 volt battery 22 to supply sufficient current over thecircuit to ground through control wire 11 to actuate change over relay20. With the actuation of change over relay 20, change over contact 20-1will open to disconnect rectifier bridge 23 from the control circuit. Itis desirable to energize rectifier bridge 23 only during the second modeof operation, when the transportable unit it powered from an externalalternating current power source receptacle. Actuation of change overrelay 20 also closes change over contact 20-2. The battery 22 is nowconnected to supply sufficient current to actuate starter relay 25 andignition coils 26. Actuating starter relay 25 closes starter contact25-1 and current is supplied to the windings of the starter-generator28. The self contained internal combustion engine has thus beenconditioned and begins to operate during the first mode of operation todrive the unit compressor and induction motor-generator 4.

As previously described, during the second mode of operation, it isdesired not to operate the self contained internal combustion engine butalternatively to power the transportable refrigeration unit from anexternal source of electric power. During the second mode of operation,power plug 6 is connected to the receptacle 10 (shown dotted in FIG. 2)preferably ofa 30, 460V, external AC power source to supply power toelectrical loads 5 and 15 and to induction motor-generator 4. Theinduction motor-generator 4 then functions as a prime mover, or, in thepreferred embodiment as an induction motor which is capable of drivingthe units compressor during the second mode. Also, during the secondmode of operation, power is supplied to rectifier'bridge 23 from controlpower transformer 29, since in the second mode of operation, the changeover relay 20 is not actuated and change over contacts 20-1 and 20-3remain in a closed position. This enables rectifier bridge 23 to supplya direct current sufficient to energize defrost relay'30 and heaterrelay 31. Actuation of relays 30 and 31 is essential in order to defrostthe refrigeration unit when heaters will be energized while the unitscompressor and fan motor 5 are not operating.

Although other features of the engine control circuit and therefrigeration unit controls are illustrated, a

detailed description of them is not considered necessary to theunderstanding of the instant invention and is therefore not made herein.

A transportable refrigeration unit has been disclosed which has twomodes of operation, the unit operating in the first mode with a selfcontained internal source of power and in the second mode from anexternal AC power source. The unit is adapted to operate in either thefirst or second modes depending primarily upon making a simpleelectrical connection between a power cable and either an attached,-selfcontained power source receptacle or an external, alternate power sourcereceptacle. This connecting operation provides the unit with both a safeand convenient means whereby users of any skill can efficiently operatethe unit in either the first or second mode of operation withoutactuating complicated or cumbersome switching arrangements.

What I claim as my invention:

ii. A transportable refrigeration unit having two modes of operation tobe powered by a first prime mover in the first mode of operation or froma receptacle of an electric power source to be connected to a secondprime mover in the second mode of operation and comprising, a firstprime mover, an induction machine operable as a generator in the firstmode of operation and as a motor to be a second prime mover in thesecond mode of operation, a mechanical load connected to be driven withsaid induction machine, an electrical load, a power cord and plug, areceptacle having passive electrical components connected thereto andattached to the transportable unit, means to connect said first primemover to said mechanical load and to said induction machine whenfunctioning as a generator in the first mode of operation and todisconnect said first prime mover from the mechanical load and saidinduction maching when functioning as a second prime mover in the secondmode of operation, means to connect said power cord to said inductionmachine and to said electrical load during the first and second modes ofoperation, said plug adapted to be received in said attached receptacleto connect said passive components to said induction machine to enablesaid induction machine to function as a generator of electric power forsaid electric load in the first mode of operation, said cord and plugbeing adapted to be con nected to the external electric power receptaclein the second mode of operation to power said electrical load and saidinduction machine therefrom for causing said induction machine tofunction as a motor and the second prime mover.

2. The invention as defined in claim 1 having means to control theoperation of said first prime mover, said attached receptacle havingmeans connected to said control means whereby said first prime mover isable to be operable only when said plug is received in said attachedreceptacle.

3. The invention as defined in claim 2 having means to control the oeration of said firstprime mover, said attached recep acle providingelec rical connections between said power cord and said prime movercontrol means for enabling said first prime mover to be operable duringthe first mode of operation.

4. The invention as defined in claim ll wherein the means for connectingthe first prime mover to said mechanical load and to said inductionmachine in the first mode of operation and for disconnecting said firstprime mover in the second mode of operation is a centrifugal clutch.

5. The invention as defined in claim 1 wherein the passive electrical,components connected to said attached receptacle are comprised of a bankof capacitors whereby said induction machine may function as a selfexcited induction generator during the first mode of operation.

1. A transportable refrigeration unit having two modes of operation tobe powered by a first prime mover in the first mode of operation or froma receptacle of an electric power source to be connected to a secondprime mover in the second mode of operation and comprising, a firstprime mover, an induction machine operable as a generator in the firstmode of operation and as a motor to be a second prime mover in thesecond mode of operation, a mechanical load connected to be driven withsaid induction machine, an electrical load, a power cord and plug, areceptacle having passive electrical components connected thereto andattached to the transportable unit, means to connect said first primemover to said mechanical load and to said Induction machine whenfunctioning as a generator in the first mode of operation and todisconnect said first prime mover from the mechanical load and saidinduction maching when functioning as a second prime mover in the secondmode of operation, means to connect said power cord to said inductionmachine and to said electrical load during the first and second modes ofoperation, said plug adapted to be received in said attached receptacleto connect said passive components to said induction machine to enablesaid induction machine to function as a generator of electric power forsaid electric load in the first mode of operation, said cord and plugbeing adapted to be connected to the external electric power receptaclein the second mode of operation to power said electrical load and saidinduction machine therefrom for causing said induction machine tofunction as a motor and the second prime mover.
 1. A transportablerefrigeration unit having two modes of operation to be powered by afirst prime mover in the first mode of operation or from a receptacle ofan electric power source to be connected to a second prime mover in thesecond mode of operation and comprising, a first prime mover, aninduction machine operable as a generator in the first mode of operationand as a motor to be a second prime mover in the second mode ofoperation, a mechanical load connected to be driven with said inductionmachine, an electrical load, a power cord and plug, a receptacle havingpassive electrical components connected thereto and attached to thetransportable unit, means to connect said first prime mover to saidmechanical load and to said Induction machine when functioning as agenerator in the first mode of operation and to disconnect said firstprime mover from the mechanical load and said induction maching whenfunctioning as a second prime mover in the second mode of operation,means to connect said power cord to said induction machine and to saidelectrical load during the first and second modes of operation, saidplug adapted to be received in said attached receptacle to connect saidpassive components to said induction machine to enable said inductionmachine to function as a generator of electric power for said electricload in the first mode of operation, said cord and plug being adapted tobe connected to the external electric power receptacle in the secondmode of operation to power said electrical load and said inductionmachine therefrom for causing said induction machine to function as amotor and the second prime mover.
 2. The invention as defined in claim 1having means to control the operation of said first prime mover, saidattached receptacle having means connected to said control means wherebysaid first prime mover is able to be operable only when said plug isreceived in said attached receptacle.
 3. The invention as defined inclaim 2 having means to control the operation of said first prime mover,said attached receptacle providing electrical connections between saidpower cord and said prime mover control means for enabling said firstprime mover to be operable during the first mode of operation.
 4. Theinvention as defined in claim 1 wherein the means for connecting thefirst prime mover to said mechanical load and to said induction machinein the first mode of operation and for disconnecting said first primemover in the second mode of operation is a centrifugal clutch.